Duophonic is a term used to refer to a sound process by which a monaural recording is reprocessed into a kind of "fake stereo" by splitting the signal into two channels, delaying the left and the right channels by means of delay lines and other circuits, desynchronizing the two channels by fractions of a second, and cutting the bass frequencies in one channel with a high-pass filter, then cutting the treble frequencies in the other channel with a low-pass filter. The result was an artificial stereo effect, without giving the listener the true directional sound characteristics of real stereo. In some cases, the effect was enhanced with reverberation and other technical tricks, sometimes adding stereo echo to mono tracks in an attempt to fool the listener.